Enteropathogenic E. coli (EPEC) and Shiga-toxigenic E. coli (STEC) are two related types of E. coli bacteria that can cause diarrhea in humans. EPEC infection is common in young children in low income, developing countries, and STEC infection, caused by E. coli 0157:H7, is often observed in developed countries like the U.S. STEC is also known as enterohemorrhagic E. coli (EHEC), and is noted for its ability to cause food-borne outbreaks of bloody diarrhea complicated by hemolytic-uremic syndrome (HUS). STEC infections are difficult to treat because antibiotics increase the production of the Shiga toxin or toxins from which this organism gets its name. As a result, current CDC guidelines recommend that persons infected with STEC not be treated with any antibiotics (http://www.cdc.gov/ecoli/). The inability to offer any type of treatment (other than oral or I.V. fluids) to patients suffering from STEC has been a source of great frustration to doctors, patients, and public health authorities. CDC and FDA efforts have been directed almost entirely toward prevention of STEC infection, with the result that almost no research has been conducted on potential therapies. The applicant's laboratory has discovered that EPEC and STEC take advantage of ATP and adenosine released from intestinal cells following pathogen-induced damage. Understanding how to harness ATP and adenosine signals using pharmacological interventions is the first part of the project, Aim 1. The second part of this application studies nitric oxide signaling in response to EPEC and STEC infection. EPEC and STEC virulence is inhibited by nitric oxide, and these E. coli pathogens have developed methods to suppress the nitric oxide (NO) pathway in host cells. Restoration of nitric oxide production by: (1) addition of a drug which releases NO; (2) addition of the amino acid arginine; or (3) stimulation with interferon-?, all have beneficial effects in an in vivo model of EPEC and STEC infection. These interventions will be tested in Aim 2. In Aim 3 we plan to select the most promising interventions from Aim 1 and Aim 2 and combine them to determine if increased protection is achieved. In addition, we will test a triple combination with added zinc. Aim 3 will also test these drugs and nutrients in non-surgically altered rabbits to determine if they enhance the immune response against the pathogens.